Issue 4, 2018

Cost-effective 17O enrichment and NMR spectroscopy of mixed-metal terephthalate metal–organic frameworks

Abstract

17O solid-state NMR spectroscopy is employed to investigate the cation disorder in metal–organic frameworks containing two different types of metal cations. Although NMR offers exquisite sensitivity to the local, atomic-scale structure, making it an ideal tool for the characterisation of disordered materials, the low natural abundance of 17O (0.037%) necessitates expensive isotopic enrichment to acquire spectra on a reasonable timescale. Using dry gel conversion and a novel steaming method we show that cost-effective and atom-efficient enrichment of MOFs is possible, and that high-resolution 17O NMR spectra are sensitive both to the structural forms of the MOF and the presence of guest molecules. For mixed-metal forms of MIL-53, NMR can also provide information on the final composition of the materials (notably different to that of the initial starting material) and the preference for cation clustering/ordering within the MOFs. For Al, Ga MIL-53, the distribution of cations results in a mixed-pore form upon exposure to water, unlike the different structures seen for the corresponding end members. This work shows that as good levels of enrichment can be achieved at reasonable cost, 17O NMR spectroscopy should be an invaluable tool for the study of these important functional materials.

Graphical abstract: Cost-effective 17O enrichment and NMR spectroscopy of mixed-metal terephthalate metal–organic frameworks

Supplementary files

Article information

Article type
Edge Article
Submitted
26 oct. 2017
Accepted
23 nov. 2017
First published
23 nov. 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 850-859

Cost-effective 17O enrichment and NMR spectroscopy of mixed-metal terephthalate metal–organic frameworks

G. P. M. Bignami, Z. H. Davis, D. M. Dawson, S. A. Morris, S. E. Russell, D. McKay, R. E. Parke, D. Iuga, R. E. Morris and S. E. Ashbrook, Chem. Sci., 2018, 9, 850 DOI: 10.1039/C7SC04649A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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